Corrosion Resistance Of Ceramic Coatings Research Articles

Effect of solution temperature on the microstructure and properties of ceramic coating on the surface of 2024 aluminum alloy

This study investigates the influence of the 2024 aluminum alloy was treated with solution before ceramic treatment on the microstructure and characteristics of ceramic coatings applied to 2024 aluminum alloy substrates. The microhardness, corrosion resistance, and microstructural properties of these ceramic coatings were assessed using a microhardness tester, an electrochemical workstation, and a scanning electron microscope. The findings indicate that pre-treatment involving solution treatment significantly enhances the hardness and corrosion resistance of 2024 aluminum alloy ceramic coatings. Notably, when the solution temperature was maintained at 460 °C, the most rapid decrease in current density was observed during the ceramization process, resulting in the attainment of the lowest final stable current density. This particular condition yielded ceramic coatings with optimal hardness and corrosion resistance, with hardness exhibiting a remarkable increase of 48.9 HV, self-corrosion potential rising by 0.207 V, and polarization resistance surging by 5310.7 Ω. Moreover, the surface of the ceramic coating displayed remarkable smoothness and was devoid of discernible defects such as cracks or looseness. In light of these findings, it can be concluded that the optimum solution temperature for achieving these desirable properties is 460 °C. This conclusion is derived from a comprehensive analysis encompassing both the morphology and corrosion resistance of ceramic coatings.

Corrosion resistance of ceramic coatings formed by microarc oxidation on aluminium alloy AK4-1

Corrosion resistance of ceramic coatings formed by microarc oxidation on aluminium alloy AK4-1

Application of some inhibitors for improving the corrosion resistance of ceramic coatings deposited on non-alloy steel by short-pulse laser treatment

Application of some inhibitors for improving the corrosion resistance of ceramic coatings deposited on non-alloy steel by short-pulse laser treatment

Preparation and Properties of Chemically Bonded Ceramic Coatings Reinforced by GO-TiO2 composites

Graphene oxide (GO) decorated by titanium dioxide (TiO2) was fabricated and introduced into the chemically bonded ceramic coatings as a nanofiller. The analysis of the results of thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electronic microscopy (SEM), and transmission electron microscopy (TEM) show that TiO2 has decorated on the surface of GO by chemical bonds. Furthermore, the effect of incorporating GO-TiO2 on properties of ceramic coatings was investigated. The results show that GO-TiO2 achieved a homogeneous dispersion and compatibility in ceramic matrix without obvious cracks. The potentiodynamic polarization test was conducted to investigate the influence of GO-TiO2 on the corrosion behavior. The results demonstrated that corrosion resistance of ceramic coatings remarkably enhanced by adding GO-TiO2. Furthermore, the anticorrosive mechanisms of ceramic coatings with GO-TiO2 were tentatively discussed.

Preparation and corrosion behavior of chemically bonded ceramic coatings reinforced with ZnO-MWCNTs composite

Zinc oxide decorated multi-walled carbon nanotubes (ZnO-MWCNTs) was synthesized by sol-gel method. The structure and morphology of ZnO-MWCNTs were characterized by x-ray diffraction analysis (XRD), and transmission electron microscopy (TEM). The results showed that ZnO was well dispersed on the surface of MWCNTs. Furthermore, ZnO-MWCNTs was added into chemically bonded ceramic coatings on stainless steel to improve its anticorrosion properties. The analysis of XRD showed that no new phase was formed with the addition of ZnO-MWCNTs. Besides, there was no cracks between MWCNTs and ceramic matrix and MWCNTs was covered by ceramic gel resulted by the reaction between the aluminum phosphate (AP) binder and ZnO on the surface of MWCNTs, which means that MWCNTs and the ceramic matrix were well connected by ceramic gel, and resulting in the perfect bonding strength. In addition, the influence of ZnO-MWCNTs on the corrosion resistance of ceramic coatings was investigated by the potentiodynamic polarization. The results indicated that the application of ZnO-MWCNTs can effectively improve the corrosion resistance of ceramic coatings. Furthermore, the anticorrosive mechanisms of ceramic coatings with ZnO-MWCNTs were tentatively discussed.

Corrosion resistance of ceramic coatings sprayed on stainless steel substrates

ABSTRACTCeramic thermal barrier coatings are being used in oil and gas industries, gas turbines and diesel engines. An atmospheric plasma spraying process is used to coat the ceramics on stainless steel grade 304 substrates. The salt spray (fog) test procedure was used to assess the corrosion resistance of ceramic-coated specimens. The coatings with ceria and without ceria on yttria-stabilised zirconia were compared for corrosion resistance. The commencement of red dust and the amount of weight loss of the coated specimens were related to time. The results indicated that the ceria mixed yttria-stabilised zirconia showed a better corrosion resistance.

Influence of Electrolyte Parameters on the Properties of the Ceramic Coatings Deposited on Aluminum Alloy by Plasma Electrolytic Oxidation

Four different types of electrolyte (aluminate, silicate, borate, and phosphate) solutions were optimized to be used for the surface treatment of aluminum alloy 7075 by plasma electrolytic oxidation. Microstructure, phase composition, and corrosion resistance of ceramic coatings on the surface were analyzed by SEM, X-ray diffraction, and electrochemical work station. It was demonstrated that ceramic coatings prepared in aluminate solution had excellent continuity and a compact structure with micro hardness of HV 0.1 = 1100 MPa. The majority of all coatings consisted of γ-Al 2 O 3 and bits of α-Al 2 O 3 . The corrosion potential was increased to a small extent, while the corrosion current density was significantly reduced.

Effect of additive Al2 O3 powders on micro-arc oxide coating of magnesium alloy

Abstract In order to understand the effect of additive Al2O3 powders on the film corrosion resistance and the microstructure of the micro-arc oxide (MAO) ceramic film of magnesium alloy, AZ91D die cast magnesium alloy was oxidized with a special micro-arc apparatus. Morphological characteristics and phase constituent of ceramic coatings were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). And the aluminum (Al) element of before and after the Al2O3 accession were analyzed by energy-dispersive X-ray (EDX). The results showed that after adding Al2O3 powders, pores on ceramic coatings decreased, the loose layer became more compact, the new phase of Al2O3 appeared, and the Al element of the ceramic membrane increased. Ultrasonic waves promoted the content of Al2O3 in the layer. Electrochemical corrosion experiments in 3.5% NaCl solution showed that the corrosion resistance of ceramic coatings after adding Al2O3 powders was improved greatly.

Effects of Electrolyte Parameters on Properties of Ceramic Coatings Formed on Aluminum Alloy 7075 by Plasma Electrolytic Oxidation

Four electrolyte (aluminate, silicate, borate and phosphate) solutions were optimized for using in surface treatment of 7075 aluminum alloy by plasma electrolytic oxidation. Microstructure, phase composition and corrosion resistance of ceramic coatings on the surface were analyzed by SEM, X-ray diffraction as well as electrochemical work station. It was showed that ceramic coatings prepared in aluminate solution had excellent continuity, compact structure with micro hardness of HV0.1 1100. The major portion of all coatings consisted of γ-Al2O3 and bits of α-Al2O3, the corrosion potential was increased by a small extent while the corrosion current density was significantly reduced.

Influences of Current Density on the Structure and Corrosion Resistance of Ceramic Coatings on ZK60 Mg Alloy by Plasma Electrolytic Oxidation

Influences of Current Density on the Structure and Corrosion Resistance of Ceramic Coatings on ZK60 Mg Alloy by Plasma Electrolytic Oxidation

Effect of PEO power modes on structure and corrosion resistance of ceramic coatings on AZ91D Mg alloy

The aim of this work is to investigate the effects of different power modes [constant current (CC), constant voltage (CV) and constant power (CP)] on the structure and corrosion resistance of the plasma electrolytic oxidation ceramic coatings containing Ca and P on AZ91D Mg alloy. The phase composition, morphology and element distribution of the coatings were studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the coatings in the simulated body fluid was examined by electrochemical impedance spectroscopy and polarisation curve methods. The results showed that the coatings were of porous structure and mainly composed of MgO. The thickness, surface roughness, the size of the surface micropores and the amount of MgO were all increased with the cell voltage under the same power mode or increased in the sequence CV>CC>CP under the different power modes. The corrosion resistance of coatings was related to the structure characteristics, which were determined by different power modes. Among the different power modes, the corrosion resistance of the coatings is generally increased in the sequence CV>CP>CC, and under the same mode, the proper increase in the cell voltage is liable for improving the corrosion resistance of the coatings.

Influences of Additive on the Formation and Corrosion Resistance of Micro-arc Oxidation Ceramic Coatings on Aluminum Alloy

The influence of Na2WO4 on the forming process and corrosion resistance of ceramic coatings was researched in silicate electrolyte system. The surface morphology and phase composition of ceramic coatings were analyzed by SEM and XRD. The results show that Na2WO4 can promote the formation of high impedance coatings, reduce the arcing-terminal voltages, and increase the thickness of ceramic coatings. When the concentration of Na2WO4 is 5 g/L, the arcing voltage is the lowest, the corrosion resistance of ceramic coatings is improved by 1.6 times compared with the ceramic coatings’ in silicate electrolyte system.

Growth Process and Corrosion Resistance of Ceramic Coatings of Micro-Arc Oxidation on Mg-Nd Magnesium Alloys

The regulation of ceramic coating formed by micro-arc oxidation on Mg-3Nd-0.2Zn-0.4Zr(wt%) magnesium alloys has been investigated by SEM and XRD. The relation of phase structure and corrosion resistance of MgO coating formed by micro-arc oxidation in different growth stages has been analyzed. The results have shown that in the initial stages of micro-arc oxidation, the growth of coating accords with linear regularity, which is the stage of anodic oxidation controlled by electrochemical polarization. With elongated treated time and increased thickness of the coating, the growth of coating accords with parabolic and linear regularity, which is the stage of micro-arc oxidation. In the stage of local arc light, the slope of parabola and thickness of loose coating increases so that the growth rate enhances. The phase structure of loose coating is mainly composed of MgSiO3 and the phase structure of compact ceramic coating is mainly composed of MgO. From the stage of micro-arc oxidation to local arc light, corrosion resistance of coating firstly increase and then decrease. The satisfied corrosion resistance corresponds to the coating time ranging from 7 to15minutes.The addition of rare earth elements in the magnesium alloy reduces the amount of smooth areas on ceramic surface. So the ceramic coating becomes more compact and smooth. The rare earth elements don’t form independent phases in ceramic coating but affect the relative proportion of constitution phases, resulting in the reduction of intermixed magnesium phase and the increase of the MgO and MgSiO3 phases.

Growth process and corrosion resistance of ceramic coatings of micro-arc oxidation on Mg-Gd-Y magnesium alloys

The regulation of ceramic coating formed by micro-arc oxidation on Mg-11Gd-1Y-0.5Zn (wt.%) magnesium alloys was investigated by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). The relation of phase structure and corrosion resistance of MgO coating formed by micro-arc oxidation in different growth stages was analyzed. The results showed that the growth of coating accorded with linear regularity in the initial stage of micro-arc oxidation, which was the stage of anodic oxidation controlled by electrochemical polarization. With elongated treated time and increased thickness of the coating, the growth of coating accorded with parabolic regularity, which was the stage of micro-arc oxidation. In contrast to the stage of anodization, the growth rate of micro-arc was slower than that in anodization. In the stage of local arc light, the slope of parabola and thickness of loose coating were increased so that the growth rate was enlarged. The phase structure of loose coating was mainly composed of MgSiO 3 and the phase structure of compact ceramic coating was mainly composed of MgO. From the stage of micro-arc oxidation to local arc light, corrosion resistance of coating was firstly increased and then decreased. The satisfied corrosion resistance corresponded to the coating time ranging from 7 to 12 min. The addition of rare earth elements in the magnesium alloy reduced the amount of smooth areas on ceramic surface. So the ceramic coating became more compact and smoother. The rare earth elements did not form independent phases in ceramic coating but affected the relative proportion of constitution phases, resulting in the reduction of intermixed magnesium phase and the increase of the MgO and MgSi 2O 4 phases.

Effects of Sodium Fluoride on Structure and Corrosion Resistance of Plasma Electrolytic Oxidation Ceramic Coatings on Magnesium Alloys

Abstract F− is used widely as an additive in the electrolyte solutions during the plasma electrolytic oxidation (PEO) of Mg alloys. The goal of this work was to investigate effects of sodium fluoride (NaF) on the structure and corrosion resistance of the ceramic coatings containing Ca and P on AZ91D (UNS M11916) Mg alloy using the PEO technique. The phase composition, morphology, and the element distribution of the coatings were studied using x-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The corrosion resistance of the coatings in the simulated body fluid (SBF) was examined using electrochemical impedance spectroscopy (EIS) and the polarizing curve methods. The results show that the coating was composed mainly of magnesium oxide (MgO), which was increased with a dosage of NaF. Ca and P also existed in the coating. The coating had a two-layer structure: the outer layer was loose and porous and the inner layer was comparatively dense. There were many microholes on the ...

Corrosion Behavior of Surfaced AM50 Magnesium Alloys under Stress Conditions

Micro-arc oxidization of AM50 magnesium alloys was studied. The influence of micro-arc oxidization process was investigated; phase structure were analyzed using X-ray diffraction (XRD). Open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion resistance of ceramic coatings formed on magnesium alloys under stress conditions. XRD analyses indicate that the ceramic coatings fabricated on the surface of magnesium alloys by micro-arc oxidization are composed of spinel phase MgAl2O4 The corrosion resistance of ceramic coatings is improved compared with magnesium alloy substrate.

Effects of Working Frequency on the Structure and Corrosion Resistance of Plasma Electrolytic Oxidation Coatings Formed on a ZK60 Mg Alloy

The effects of working frequency on the composition, morphology, and corrosion resistance of ceramic coatings formed on a ZK60 magnesium alloy by plasma electrolytic oxidation were studied in this paper. It is found that the coatings are composed of MgO only. The rise of frequency led to an increase in the number of the channels and a decrease in the discharge channel diameter. The corrosion resistance of the coated samples was improved compared with that of substrate, which became more obvious as the working frequency was increased. This could be due to the more compact structure of the alloy formed at higher frequencies.

Effects of cathode current density on structure and corrosion resistance of plasma electrolytic oxidation coatings formed on ZK60 Mg alloy

Current density is a key factor in plasma electrolytic oxidation (PEO) process. The aim of this paper is to study the effects of cathode current density on the composition, morphology, and corrosion resistance of ceramic coatings on ZK60 magnesium alloy prepared through bi-polar plasma electrolytic oxidation in Na 3PO 4 solution. The phase composition, morphology, and corrosion resistance were studied by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization in 3.5% NaCl solution. It is found that the as-produced coatings are only composed of MgO. The increase of cathode current density made the coatings less porous and more compact. Analysis of EIS and potentiodynamic polarization technique on the samples shows that the corrosion resistance of the coated samples is better than that of ZK60 magnesium alloy, and that a bigger cathode current density can improve the corrosion resistance of as-prepared coatings.

Influences of Duty Ratio on Structure and Corrosion Resistance of Ceramic Coatings on Ti-6Al-4V by Micro-Plasma Oxidation

Duty ratio is a key factor during micro-plasma oxidation process. Its influences on structure and corrosion resistance of ceramic coatings on Ti–6Al–4V by pulsed bi-polar MPO in NaAlO2 solution were investigated. The ceramic coatings were composed of Al2TiO5, α-Al2O3 and rutile TiO2, of which Al2TiO5 was the main crystalline. The coating can be divided into a porous outer layer and a dense inner layer. Compared with the condition of the same duty ratio for both pulses, the rise of anode duty ratio (D1) led to an increase in the amount of Al2TiO5 and α-Al2O3 and increased the thickness of the coating; whereas the rise of cathode duty ratio (D2) led to a decrease in the amount of α-Al2O3 and decreased the thickness of the coating. Besides, the corrosion resistance of the coated samples was better than that of Ti-6Al-4V substrate. When D1 / D2 = 60 / 30, the produced coating’s corrosion resistance was best.

Influence of the frequency on the structure and corrosion resistance of ceramic coatings on Ti–6Al–4V alloy produced by micro-plasma oxidation

The influence of the working frequency on the structure, morphology and corrosion resistance of ceramic coatings on Ti–6Al–4V by pulsed bi-polar micro-plasma oxidation in NaAlO 2 solution has been studied. The produced coatings were composed of Al 2TiO 5, α-Al 2O 3 and rutile TiO 2, of which Al 2TiO 5 was the main crystalline phase. An increase in frequency did not change the content of Al 2TiO 5, however, the content of rutile TiO 2 increased gradually while the content of α-Al 2O 3 decreased drastically. The coating can be divided into two layers: a porous outer layer and a dense inner layer. The thickness of the coatings reduced as the frequency increased. The corrosion potential increased with decreasing working frequency. The corrosion current density of the coated samples decreased with decreasing working frequency up to 60 Hz and then increased with further decrease of the frequency. Therefore, the best corrosion resistance was attained in the coated sample, which was prepared under the frequency of 60 Hz.